(define (extend-env* var-list val-list env)
    (if (null? var-list)
        env
        (extend-env*
            (cdr var-list)
            (cdr val-list)
            (list 
                (list (car var-list) (car val-list))
                env
            )
        )
    )
)


(define (report-invalid-variable s)
    (eopl:error ’has-binding? "Bad : ~s" s)
)
